John McCabe has started a very interesting thread the Ariane 5 failure. You can find it here.
One of the really interesting links to emerge from this thread, is the official report on what caused the accident. From the conclusion we get this:
The failure of the Ariane 501 was caused by the complete loss of guidance and attitude information 37 seconds after start of the main engine ignition sequence (30 seconds after lift- off). This loss of information was due to specification and design errors in the software of the inertial reference system.
The extensive reviews and tests carried out during the Ariane 5 Development Programme did not include adequate analysis and testing of the inertial reference system or of the complete flight control system, which could have detected the potential failure.
So there you have it: It was not casued by Ada. This most unfortunate and horrible accident happened because of bad specs and design errors.
The entire report is very interesting, if you’re into this sort of thing.